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PRIOR ANALYTICS
by Aristotle
translated by A。 J。 Jenkinson
Book I
1
WE must first state the subject of our inquiry and the faculty to
which it belongs： its subject is demonstration and the faculty that
carries it out demonstrative science。 We must next define a premiss； a
term； and a syllogism； and the nature of a perfect and of an imperfect
syllogism； and after that； the inclusion or noninclusion of one term
in another as in a whole； and what we mean by predicating one term
of all； or none； of another。
A premiss then is a sentence affirming or denying one thing of
another。 This is either universal or particular or indefinite。 By
universal I mean the statement that something belongs to all or none
of something else； by particular that it belongs to some or not to
some or not to all； by indefinite that it does or does not belong；
without any mark to show whether it is universal or particular； e。g。
'contraries are subjects of the same science'； or 'pleasure is not
good'。 The demonstrative premiss differs from the dialectical； because
the demonstrative premiss is the assertion of one of two contradictory
statements （the demonstrator does not ask for his premiss； but lays it
down）； whereas the dialectical premiss depends on the adversary's
choice between two contradictories。 But this will make no difference
to the production of a syllogism in either case； for both the
demonstrator and the dialectician argue syllogistically after
stating that something does or does not belong to something else。
Therefore a syllogistic premiss without qualification will be an
affirmation or denial of something concerning something else in the
way we have described； it will be demonstrative； if it is true and
obtained through the first principles of its science； while a
dialectical premiss is the giving of a choice between two
contradictories； when a man is proceeding by question； but when he
is syllogizing it is the assertion of that which is apparent and
generally admitted； as has been said in the Topics。 The nature then of
a premiss and the difference between syllogistic； demonstrative； and
dialectical premisses； may be taken as sufficiently defined by us in
relation to our present need； but will be stated accurately in the
sequel。
I call that a term into which the premiss is resolved； i。e。 both the
predicate and that of which it is predicated； 'being' being added
and 'not being' removed； or vice versa。
A syllogism is discourse in which； certain things being stated；
something other than what is stated follows of necessity from their
being so。 I mean by the last phrase that they produce the consequence；
and by this； that no further term is required from without in order to
make the consequence necessary。
I call that a perfect syllogism which needs nothing other than
what has been stated to make plain what necessarily follows； a
syllogism is imperfect； if it needs either one or more propositions；
which are indeed the necessary consequences of the terms set down； but
have not been expressly stated as premisses。
That one term should be included in another as in a whole is the
same as for the other to be predicated of all of the first。 And we say
that one term is predicated of all of another； whenever no instance of
the subject can be found of which the other term cannot be asserted：
'to be predicated of none' must be understood in the same way。
2
Every premiss states that something either is or must be or may be
the attribute of something else； of premisses of these three kinds
some are affirmative； others negative； in respect of each of the three
modes of attribution； again some affirmative and negative premisses
are universal； others particular； others indefinite。 It is necessary
then that in universal attribution the terms of the negative premiss
should be convertible； e。g。 if no pleasure is good； then no good
will be pleasure； the terms of the affirmative must be convertible；
not however； universally； but in part； e。g。 if every pleasure；is good；
some good must be pleasure； the particular affirmative must convert in
part （for if some pleasure is good； then some good will be
pleasure）； but the particular negative need not convert； for if some
animal is not man； it does not follow that some man is not animal。
First then take a universal negative with the terms A and B。 If no B
is A； neither can any A be B。 For if some A （say C） were B； it would
not be true that no B is A； for C is a B。 But if every B is A then
some A is B。 For if no A were B； then no B could be A。 But we
assumed that every B is A。 Similarly too； if the premiss is
particular。 For if some B is A； then some of the As must be B。 For
if none were； then no B would be A。 But if some B is not A； there is
no necessity that some of the As should not be B； e。g。 let B stand for
animal and A for man。 Not every animal is a man； but every man is an
animal。
3
The same manner of conversion will hold good also in respect of
necessary premisses。 The universal negative converts universally； each
of the affirmatives converts into a particular。 If it is necessary
that no B is A； it is necessary also that no A is B。 For if it is
possible that some A is B； it would be possible also that some B is A。
If all or some B is A of necessity； it is necessary also that some A
is B： for if there were no necessity； neither would some of the Bs
be A necessarily。 But the particular negative does not convert； for
the same reason which we have already stated。
In respect of possible premisses； since possibility is used in
several senses （for we say that what is necessary and what is not
necessary and what is potential is possible）； affirmative statements
will all convert in a manner similar to those described。 For if it
is possible that all or some B is A； it will be possible that some A
is B。 For if that were not possible； then no B could possibly be A。
This has been already proved。 But in negative statements the case is
different。 Whatever is said to be possible； either because B
necessarily is A； or because B is not necessarily A； admits of
conversion like other negative statements； e。g。 if one should say；
it is possible that man is not horse； or that no garment is white。 For
in the former case the one term necessarily does not belong to the
other； in the latter there is no necessity that it should： and the
premiss converts like other negative statements。 For if it is possible
for no man to be a horse； it is also admissible for no horse to be a
man； and if it is admissible for no garment to be white； it is also
admissible for nothing white to be a garment。 For if any white thing
must be a garment； then some garment will necessarily be white。 This
has been already proved。 The particular negative also must be
treated like those dealt with above。 But if anything is said to be
possible because it is the general rule and natural （and it is in this
way we define the possible）； the negative premisses can no longer be
converted like the simple negatives； the universal negative premiss
does not convert； and the particular does。 This will be plain when
we speak about the possible。 At present we may take this much as clear
in addition to what has been said： the